How to compute the percentage of difference between two plots?

Hi, Could anyone please tell me how to calcute the percentage of difference between two plots? Actually I'm trying to see if there is any model error between two plots or in other words, how much they deviate from each other.

I have come across some functions like rms, R-square fit etc. But I don't have any idea on using them. Please help me with this.

Answer 1

[Image Analyst]

What's wrong with the obvious:

deltaSignal = abs(testSignal - referenceSignal);
percentageDifference = deltaSignal ./ referenceSignal; % Percent by element.
meanPctDiff = mean(percentageDifference); % Average percentage over all elements.

[Priya]

Sorry, I think I'm making a mistake in the plot command. If you can please tell me how does the plot command looks like for the answer mentioned above.

[Ella]

Is the final answer already in Percentage ? or we still need to times by 100 ?

[Image Analyst]

It's a fraction between 0 and 1. To get a percentage in the range 0-100, you'd need to multiply by 100.

[Aravind Bolisetty]

Hi, This is valid only if the vectors are of same length. What if the vectors are of different lengths?

Eg: I have data for a function f(x) where x is between (0,1). I obtained a result v(x) at 1000 steps of x in (0,1) and I need to compare it with w(x) which is the exact result. I have data fro w(x) at 100 steps of x in (0,1). I can look at the plots and say, they're probably close, but I need to say that mathematically to be confident. Thank you.

[Image Analyst]

Use interp1() or spline() to upsample the signal with fewer elements so that it has the same number of elements as the other signal.

[Harish Dhanasekaran Velayutha Rajan]

is this a measure of weighted error ? Whats the statistical term for this error ?

[Image Analyst]

Mean Absolute Percentage Error: https://en.wikipedia.org/wiki/Mean_absolute_percentage_error

[metehan yayla]

What if the "referenceSignal" is zero at some element(s)? Then, percentageDifference will be infinity which results in infinite meanPctDiff.

[Image Analyst]

Correct.

Answer 2

[Daniel Simmons]

To get the error between the 2 plots, you can use the compare the raw data using the relError function found at <http://uk.mathworks.com/matlabcentral/fileexchange/47834-relerror-m>